The present invention relates to a channel estimation method, and more particularly, to a channel estimation method and associated device for estimating both the pilot channel and data channel of data resource element.
In communication systems such as the third Generation Partnership Project (3GPP) Long Term Evolution (LTE) (hereinafter “LTE”), variations in phase and amplitude are introduced into signals transmitted along the channel. These variations can be realized as channel response. The channel response is usually frequency-dependent and time-dependent. If the receiver can correctly detect the channel response, channel degradation in the received signal can be compensated. Detection of the channel response is called channel estimation. In the LTE system, a number of resource elements (REs) are chosen to carry pilot signals for channel estimation purposes. The pilot signals contain useful information which facilitates the channel estimator in order to detect the channel response of a specific frequency and time. These resource elements carrying the pilot signals are also called pilot resource elements.
Due to heavy data traffic involved in wireless communication techniques, how to effectively estimate data channels of the data resource elements has become an important issue. Estimating the data channels of data resource elements is important for the recovery of the transmitted information data at the receiver to thereby reach high receiving quality. There is usually a tradeoff between hardware complexity and the channel estimation accuracy, however. For example, in the LTE system, pilot channels are already defined in the specification, and therefore the channel estimation schemes of the receiver must be designed to take advantage of available pilot channels as much as possible. Although the accuracy of the estimation results of some traditional channel estimation techniques is acceptable, the hardware scheme of these techniques may be too complex to be implemented, or may raise the cost significantly.
Please refer to FIG. 1, which is a diagram illustrating a prior art channel estimation method performed upon a time-frequency domain 100, wherein the x-axis represents the time domain, and the y-axis represents the frequency domain. As shown in FIG. 1, the time-frequency domain 100 includes a plurality of pilot resource elements represented by the time-frequency grids H0-H17 aligned in both the time direction and the frequency direction. The pilot resource elements H0-H17 are utilized to estimate the data channel of the data resource element (i.e. the grid RE1) by performing a two-dimensional (2D) channel estimation, wherein the data resource element RE1 is calculated by interpolating all of the pilot channels H0-H17. Although the above operation may improve the performance of the channel estimation, a relatively large ROM/RAM size is required. For example, each data resource element is estimated by performing a plurality of multiplication operations (18 multiplication operations are required for estimating each data resource element), which thereby increases the computational complexity thereof.
There is a need for a novel channel estimation method that can improve the channel estimation performance without significantly raising the cost.